BS/EN 304-2017 pdf download.Heating boilers – Test code for heating boilers for atomizing oil burners.
6.8.1 General
To determine the efficiency at a load corresponding to 30 % of the nominal heat output, or the arithmetic mean of the maximum and minimum heat output for range-rated boilers, one of the following methods shall be used:
The boiler is operated as for the determination of the useful efficiency at nominal heat input or at the arithmetic mean of the maximum and minimum heat input in the case of range-rated boilers.
Throughout the test, the water volume rate is maintained constant within ± 1 %, taking into account the
temperature variations, and the pump operates continuously.
The efficiency shall be determined on the basis of the net caloriflc value NCV
The direct method according to 6.5.4.1 shall be applied.
6.8.2 Efficiency at 30 %- Method 1 (time dependent method)
The boiler is installed as described in A.4, fitted to the thermally insulated test rig shown schematically in Figure 2 or Figure 3 (or any other test rig giving at least comparable results and equivalent measurement accuracies).
For standard boilers, the return temperature is held constant at (47 ± 1 °C), with a maximum variation in this temperature during the measurement period of± 1 K. For low temperature boilers the test is carried out at (37 ± 1) °C and for condensing boilers the test is carried out at (30 ± 1) °C.
If the boiler control does not permit operation at a return temperature as low as 47 °C the test is made with the lowest return temperature compatible with the operation of the boiler.
A timer is connected to the terminals of the room thermostat so as to obtain a complete operating cycle of 10 mm.
The shutdown and operating times are calculated as indicated in Table 1.
The temperatures are measured continuously directly on the flow and return of the boiler.
The boiler is considered to be in thermal equilibrium when the efficiency measurement of three consecutive cycles, combining any two results from three, does not vary by more than 0,5 percentage points. In this case, the result is equal to the average value of at least three consecutive measurement cycles. For any other case, the average value shall be calculated from at least 10 consecutive cycles.
The respective fuel and water consumption’s over complete cycles are measured. Temperatures t and tz are measured continuously.
The heat output P and the heat input QB as calculated according to Annex A. A variation of± 2 % points, with respect to the 30 % of the nominal heat output is permitted. For variations up to ± 4 % points, it Is necessary to carry out two measurements, one above and one below 30 % of the nominal heat output.
The efficiency corresponding to 30 % is determined by linear interpolation.
6.8.3 Efficiency at 30 %- Method 2 (load dependent method)
The boiler is installed as described in A.4, fitted to the thermally insulated test rig shown schematically in Figure 2 or Figure 3 (or any other test rig giving at least comparable results and equivalent measurement accuracy’s).
The boiler flow and return temperatures and the operating on and off cycles are given by the boiler control when a heat input leading to a heat output of the boiler of (30 ± 2) % of the nominal heat output (or the arithmetic mean of the maximum and minimum output for range-rated boilers) is drawn through the heat exchanger.
The temperatures are measured continuously at the flow and at the return of the boiler.
The average water temperature shall be no less than 50 °C for standard boilers and 40 °C for lowtemperature boilers. For condensing boilers a return temperature of 30 °C has to be set.
If the boiler control does not permit operation at a return temperature as low as 50 °C, the test is carried out at the lowest return temperature compatible with the operation of the boiler.
The boiler is considered to be in thermal equilibrium when the efficiency measurement of three consecutive cycles, combining any two results from three, does not vary by more than 0,5 %. In this case, the result is equal to the average value of at least three consecutive measurement cycles. For any other case, the average value shall be calculated from at least 10 consecutive cycles.
The respective fuel and water consumption’s over complete cycles are measured. The efficiency is determined using the formula in 6.5.4.1.
A variation of± 2 % points with respect to the 30 % of the nominal heat output is permitted. For
variations up to ± 4 % points, It is necessary to carry out two measurements, one above and one below
30 % of the nominal heat output.BS/EN 304-2017 pdf download.